This invention relates generally to furnaces for handling hot powder material preforms and hot refractory grain. More particularly it concerns far-reaching improvements in such furnaces enabling them to operate more efficiently, with much higher production rates, in consolidating the powder material parts surrounded by the pressurized grain to full density, to controlled shape or shapes, and with desired physical properties.
Specific needs and requirements of consolidation processes that conventional furnaces cannot meet, or have substantial difficulty in meeting, includes the following:
(1) Providing an assured very high purity atmosphere through all operation steps, including transfers between steps, to prevent oxidation or other gas contamination of the powder preforms that can damage final product purity and properties;
(2) Providing an assured close control over product temperatures through the various consolidation process steps, to obtain consistent full densities and properties in the final consolidated products;
(3) Providing highly compact design of heating and transfer system for minimum space requirements, and at minimum cost;
(4) Providing a system with highly reliable handling and transfer of products and materials through process steps requiring close process control;
(5) Providing high operating efficiences in terms of:
(a) Energy use--for heating, cooling, material recycling and process actuation; PA1 (b) Gas atmosphere use--for minimum use of gas and/or minimum contaimination thereof; PA1 (c) Start-up and shut-down times--can be held to a minimum, usually measured in minutes; PA1 (d) Heat transfer to product--fast through close proximity of transfer surfaces;
(6) Providing convenient, fast transfer of products through all process steps;
(7) Providing for continual processing products and materials through sequential steps, which is particularly useful with smaller products; or for processing single product at a time through process steps, which may be advantageous with larger products;
(8) Providing repetitive precision control over product orientation and position through all process steps and with a wide range of product sizes and shapes;
(9) Providing the capability for effectively handling products ranging in size from less than a pound up to thousands of pounds, in a variety of shapes.
Prior standard or conventional furnaces designs were incapable of meeting the above requirements, and were not economically adapted to meeting high volume production heating and handling needs in metal powder consolidation processes. In particular, they did not provide the following improvements characterized by applicant's method and apparatus:
(1) Equipment and operations that are low in cost relative to competitive technology, are compact in design, and reliable in function;
(2) Efficient overall production capability that provides for handling an extensive range of product sizes, shapes and materials not possible before;
(3) An assured high level of product quality in terms of purity, properties and shape control;
(4) Flexibility for either continual or single product processing;
(5) Fast and efficient heating of charge materials while maintaining high purity protective atmospheres around the charge materials and in the furnace system.